CHEMICAL AND DYNAMICAL GEOLOGY. 'J'J 



precipitation must have been immensely greater. In addition to the mechanical ero- 

 sion, a mighty chemical action must have begun which, assisted by the heat from 

 beneath, probably surpassed anything our fancy can picture. A half bushel of 

 unslaked lime, when treated with the proper amount of water, generates heat 

 enough to set on fire dry wood that may be in contact with it. How great then 

 must have been the chemical action when these liquid acids were first brought in 

 contact with the earth. It has sometimes appeared to me that it would have been 

 impossible for this primitive crust to be so acted upon as to furnish material suffi- 

 cient for sediments to bury it so deeply that no portion of it can now be found • 

 but this trouble entirely vanished when I considered the immense acid floods that 

 must have fallen on this primitive crust which was already of an irregular con- 

 tour. The action of the acids would not have ceased until their affinities were 

 satisfied. The chlorine would then mostly exist in the form of chlorides of so- 

 dium, calcium and magnesium ; the sulphur in the form of sulphates. Sulphides 

 could not then exist, because the sulphur had been oxidized. Great quantities 

 of silica would be left uncombined by these actions, the bases of the silicates hav- 

 ing united with the stronger acids. This would furnish quartz for the many sand- 

 stone deposits so common in all geologic ages. Soon after rain began to fall the 

 atmosphere would be reduced to about its present condition, with the exception 

 of the large amount of carbon di-oxide that it would contain. In comparison 

 with chlorhydric acid this gas is but slightly soluble in water, and would therefore 

 be removed from the air much more slowly. Perhaps this is a proper place to re- 

 mark that the question of the source of the carbon and the oxygen of the earth is 

 a very perplexing one to all speculators. We can only conceive that everything 

 was oxidized to the greatest extent in primitive times. Hence the deoxidation 

 caused by the growth of plants and the reduction of sulphates to sulphides would 

 have liberated great quantities of oxygen. So far as we now know, the only 

 ways for oxygen to be removed from the air are the oxidation of organic matter, 

 the change of binary to ternary compounds, and the change of certain " ous" 

 salts to the " ic" condition. But this is only replacing it where it originally be- 

 longed, so that it really is removing nothing from the sum total of the oxygen 

 in the air. It has been estimated by different scientists that if the carbonaceous 

 matter now in the earth has been reduced from carbon dioxide, it must have 

 liberated more than twice the amount of oxygen now in the air. But the amount 

 of pure carbon now in the earth is almost insignificant in comparison with the 

 total in the form of carbonates. Hunt has estimated that if the whole amount 

 of carbon now in the earth were liberated in the form of carbon di-oxide, the gas 

 would equal in weight two hundred times the present atmosphere. The question 

 naturally arises, whence this vast amount of gas ? In considering this question 

 Hunt says : " We are thus forced to one of two conclusions : either the wholly 

 improbable one that the atmosphere since the appearance of organic life on the 

 earth has been one of nearly pure carbonic di-oxyd, and of such immense extent 

 that the pressure at the surface would have sufficed at ordinary temperatures, for 



